xargs -- construct argument list(s) and execute utility
xargs [-0opt] [-E eofstr] [-I replstr [-R replacements]] [-J replstr]
[-L number] [-n number [-x]] [-P maxjobs] [-s size]
[utility [argument ...]]
The xargs utility reads space, tab, newline and end-of-file delimited
strings from the standard input and executes utility with the strings as
Any arguments specified on the command line are given to utility upon
each invocation, followed by some number of the arguments read from the
standard input of xargs. The utility is repeatedly executed until standard
input is exhausted.
Spaces, tabs and newlines may be embedded in arguments using single
(`` ' '') or double (``"'') quotes or backslashes (``\''). Single quotes
escape all non-single quote characters, excluding newlines, up to the
matching single quote. Double quotes escape all non-double quote characters,
excluding newlines, up to the matching double quote. Any single
character, including newlines, may be escaped by a backslash.
The options are as follows:
-0 Change xargs to expect NUL (``\0'') characters as separators,
instead of spaces and newlines. This is expected to be used in
concert with the -print0 function in find(1).
Use eofstr as a logical EOF marker.
Execute utility for each input line, replacing one or more occurrences
of replstr in up to replacements (or 5 if no -R flag is
specified) arguments to utility with the entire line of input.
The resulting arguments, after replacement is done, will not be
allowed to grow beyond 255 bytes; this is implemented by concatenating
as much of the argument containing replstr as possible, to
the constructed arguments to utility, up to 255 bytes. The 255
byte limit does not apply to arguments to utility which do not
contain replstr, and furthermore, no replacement will be done on
utility itself. Implies -x.
If this option is specified, xargs will use the data read from
standard input to replace the first occurrence of replstr instead
of appending that data after all other arguments. This option
will not effect how many arguments will be read from input (-n),
or the size of the command(s) xargs will generate (-s). The
option just moves where those arguments will be placed in the
command(s) that are executed. The replstr must show up as a distinct
argument to xargs. It will not be recognized if, for
instance, it is in the middle of a quoted string. Furthermore,
only the first occurrence of the replstr will be replaced. For
example, the following command will copy the list of files and
directories which start with an uppercase letter in the current
directory to destdir:
/bin/ls -1d [A-Z]* | xargs -J % cp -rp % destdir
Call utility for every number lines read. If EOF is reached and
fewer lines have been read than number then utility will be
called with the available lines.
Set the maximum number of arguments taken from standard input for
each invocation of utility. An invocation of utility will use
less than number standard input arguments if the number of bytes
accumulated (see the -s option) exceeds the specified size or
there are fewer than number arguments remaining for the last
invocation of utility. The current default value for number is
-o Reopen stdin as /dev/tty in the child process before executing
the command. This is useful if you want xargs to run an interactive
Parallel mode: run at most maxprocs invocations of utility at
-p Echo each command to be executed and ask the user whether it
should be executed. An affirmative response, `y' in the POSIX
locale, causes the command to be executed, any other response
causes it to be skipped. No commands are executed if the process
is not attached to a terminal.
Specify the maximum number of arguments that -I will do replacement
in. If replacements is negative, the number of arguments in
which to replace is unbounded.
Set the maximum number of bytes for the command line length provided
to utility. The sum of the length of the utility name, the
arguments passed to utility (including NULL terminators) and the
current environment will be less than or equal to this number.
The current default value for size is ARG_MAX - 4096.
-t Echo the command to be executed to standard error immediately
before it is executed.
-x Force xargs to terminate immediately if a command line containing
number arguments will not fit in the specified (or default) command
If utility is omitted, echo(1) is used.
Undefined behavior may occur if utility reads from the standard input.
The xargs utility exits immediately (without processing any further
input) if a command line cannot be assembled, utility cannot be invoked,
an invocation of utility is terminated by a signal, or an invocation of
utility exits with a value of 255.
The xargs utility exits with a value of 0 if no error occurs. If utility
cannot be found, xargs exits with a value of 127, otherwise if utility
cannot be executed, xargs exits with a value of 126. If any other error
occurs, xargs exits with a value of 1.
echo(1), find(1), execvp(3)
The xargs utility is expected to be IEEE Std 1003.2 (``POSIX.2'') compliant.
The -J, -o, -P and -R options are non-standard FreeBSD extensions
which may not be available on other operating systems.
The xargs command appeared in PWB UNIX.
If utility attempts to invoke another command such that the number of
arguments or the size of the environment is increased, it risks execvp(3)
failing with E2BIG.
FreeBSD 5.2.1 May 7, 2001 FreeBSD 5.2.1 [ Back ]